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Motor Unit Fault on Meade DSX 90


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#1 securitahh

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Posted 28 September 2015 - 05:27 PM

When I switch on the power, the handbox says:

 

©06 Meade[43E]

A U T O S T A R

 

and it makes a buzz/beep noise, then it says:

 

Press 0 to Align

or MODE for Menu

 

then after I press either of those it says

 

Testing Motors

 

and it moves up a little and pauses, then moves right/clockwise a little and pauses, then:

 

Motor Unit Fault

(etc. etc. etc.)

 

Now I should mention that the arrow-keys and motors DO work as far as moving it Up/Down/Left/Right as well as changing the slew speed with the number keys after that error (or if I just begin to navigate before pressing 0 or MODE.)  I can move the scope using the handbox, and did enjoy viewing the super-harvest-full-blood moon last night.

 

In trying to resolve this I did change the CR2032 clock battery to one with proper voltage, and the 8 AA cells I used are brand-new alkaline batteries which test at over 12v when in series so I think they're OK.  

 

I'm wondering if I just have a bad HBX cable.  I tried to do some research about trying to use a CAT5 RJ-45 computer networking cable instead, and from what I understand you'd need to use a crossover cable like would be used to connect two computers directly to each other rather than a straight-through cable that is typically used with connecting the PC to a switch or router.

 

I'd also read something to the effect that since telephone RJ-11 cables are all the same in this regard [meaning straight-through vs. crossover] then maybe one of those could be used.  I'm not sure if the handbox will work in the AUX port on the scope, though they both seem to have connections for both types of plugs.

 

 

If I am holding the ENTER and Scroll-Down keys when I turn on the power it says:

 

FLASH LOAD 3.0

 READY

 

I'm not sure which model of Autostar handbox this is, but I don't seem to have the RS-232 thing.

 

I took this telescope and the accessories out of a sealed box on 9/26/2015 and everything looked like it was all brand-new and factory sealed, inside and out.  The only thing which might make me question if it was unused or not is that the initial message from the handbox was what I wrote above, and I think I've read somewhere that there might be some sort of initialization process that one might expect from a new handbox.  It does have a signed "PASS" sticker on it indicating a good QA/QC check, however.

 

I've tried adjusting tightness of the Altitude Lock and Base Lock Knob, not sure if that matters.

 

Anyway, this leaves me with a few questions so I thought I'd try checking out this forum.

 

 What model of Autostar/handbox comes with this scope?  Or how can I determine which it is?

 Would a simple 4-conductor RJ11 telephone cord replace the HBX cable, hypothetically?

 Does a simple straight-through or crossover-type RJ45 replace the HBX cable, and if so, which?

 

Any assistance appreciated,

 

thanks in advance!



#2 MistrBadgr

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Posted 29 September 2015 - 02:31 AM

Hello, and welcome to the forum!

I guess, the first step is to get you to describe some things to me.

I need to determine whether you have a DS Generation 1 or Generation 2 mount, which will tell me something about the scope's age. Is both the base and the arm of the mount black, or is one or the other some other color? There is a strip running around the mount base with numbers, representing hours on it. What color is that strip?

Just to get it straight in my mind what you have, on the handset, is there two places to plug a cord into the end of the handset? With the program version you mentioned, I am thinking you have a 497 handset, but lets make sure. If there is just a cord coming out of the handset that you cannot unplug and no other port on the handset, then it is a 494. If it has the second socket, then it is a 497.

As a comment, if the scope will run at all after the motor fault signal, you might try running the scope around some with the arrow buttons to help spread lubrication around the gears.

On the cable running from the handset to the mount, one pair of the wires reverse positions from one end of the cord to the other. Unless there is really something wrong with the cable, the problem there can be bits of corrosion that have developed over the years in the contacts with it just sitting there. This scope has been around for a while. Try unplugging and plugging in the cable many times at each connection point.

Do not plug anything into that second port on the mount. That is for a special auxiliary connection. Most things plugged into that port can fry something on the main board.

It has been a while since I have thought about a DS mount, even though I used to be able to just about pull one apart and put it back together in my sleep, we can probably work through the easier things.

Hope some of this helps!

Bill Steen
Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 securitahh

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Posted 29 September 2015 - 05:03 PM

Hello Bill and thank you for assisting!
 
To answer your questions, both the base and the arm are black.  Also the hours strip is black.
 
The handbox and the base both have 2 differently-sized places to plug in a cord.
 
Guessing that means I have a 497 model handbox then, that's good to know.
 
Wasn't sure how long it'd been sitting around in the box, but judging from the copyright date shown on the HBX readout and on page 3 of the manual, I guess it could be from as far back as 2006.
 
Trying your suggestions with plugging/unplugging a lot and slewing a lot to spread the grease.
 
I notice that it moves at about the same speed whether I've got it set to the slowest or fastest slew rate.  Maybe that's an indication of something.  At random times it speeds up for a moment and then goes back to the common speed.
 
Yes that's most helpful.  I'm starting to think that it might be an issue of needing to add grease.  I might have to find out which type of grease to use and get to opening it up.


#4 MistrBadgr

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Posted 29 September 2015 - 06:47 PM

Eventually, the grease does seem to evaporate. I have used two different types with success. The first was just a good simply teflon spray, like Elmers. You do not what a spray teflon that has a lot of other lubricants in it. I have no idea why, but that kind seems to bog the gear train down. I have also used just a good general purpose grease, fairly light, that comes in a squeeze tube. I have also used some that had a white material in it that I think was a lithium compound of some sort that I got at an auto parts store. With grease, you just want to touch each gear with a cotton swab with a little grease on it in a couple places if you can. Run the gears fairly slow for a while to smooth out the grease. Running the gear train at high speed with a lot of grease on it just sprays grease everywhere.

You definitely have a generation 1 mount. I have a bunch of posts buried way back in the DS posts from many years ago when I was going through my mounts learning about them. At one time, I had two mounts and decided to buy two more from Meade. Then, send two in each year for maintenance. I found out later that they started just swapping them out for the repair price. I had one brand new one that was a bit jerky at very slow speeds and took it apart as my guinea pig. After many times of taking it apart and putting it back together, I finally decided not to take it apart any more or it might just fall apart. I did learn a lot, ended up actually sanding on gear teeth to get a little more play in them, and it is now a really sweet running machine whenever I use it.

One thing you right off: Underneath the battery holder, you will see a bolt head, a washer, then the edges of a brown plastic bushing. Unscrew the bolt. It is what holds the bottom bell on, but don't pull the bell off until you are really ready to go into the bottom part. Lift up the washer and inspect the plastic bushing, there may be scratches in the top face. Clean off any particles or slivers and dab a little grease on that surface. Look at the washer. It is just a stamped washer with a rough edge that is generally facing downward. The rough edge from the stamping process cuts into the plastic. You can actually cut slivers loose from the plastic that can jam the azimuth drive. To remedy this, either file that edge smooth or just turn the washer over so that the rough edge faces away from the plastic. Put a little tiny bit of grease on the washer and put it in place. Reinstall the bolt, but do not really tighten it. Finger tight is generally good enough to hold things together. You might tweak it a bit tighter with a socket wrench, but not very much....just enough to hold it in place. Sometimes, they would tighten that bolt down to actually push the two parts together and get it too tight, which can make more drag on the motor system and cause the amps to go up on the motors, making the system fault.

The motors themselves are rated for 12 volts. I built an adapter from Radio Shack parts for my mounts and then used 12 volt power supplies to drive the mounts. They do so with much more authority and do not seem to work with a quivery whine. If you do something like that, you have to think like a battery and get the polarity right. If you get positive and negative backwards, it will burn out the board and ruin the mount.

Hope this gives you some insights.

Bill Steen
Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#5 securitahh

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Posted 26 December 2015 - 11:34 AM

Yes, thank you for the expert advice.

 

Nothing seems to have solved the motor fault error, so far.  I flipped that washer over, like you suggested, and then went into the base to apply some white lithium grease using a cotton swab.

 

Everything seemed about the same, after reassembling and testing it again.  Then it occurred to me that there must also be some gears and such at the higher end of the arm, where it drives the zenith/altitude movement.  I took that apart and actually sprayed some lubricant in there rather than just dabbing it on.

 

Again everything seemed to behave about the same as before, upon putting it back together.  Just to be certain that I was using enough grease, I opened up the mount bell a second time and applied lubricant more liberally.

 

I ran the motors a lot and then tried using a much more powerful 12v supply as well.  The bigger power supply did make an observable difference in the sound of the motors running, and the power-on LED didn't seem to dim like it did with just the AA batteries for power.  The motor unit fault error message remained the same, though.

 

There were a couple things I noticed this time around which I hadn't noticed in September, whether or not anything's changed.

 

First, I noticed that the speed setting didn't seem to have any effect until after pressing "mode" and getting the "Motor Unit Fault" error.  It simply moved at max speed.  Even after the test and error message, the speed setting seems to effect only the vertical movement, while the horizontal/azimuth drive still operated at max speed regardless of the chosen setting.  This could be perfectly normal, but it seemed curious.

 

Second, I noticed that if I am moving it much for a time after it's already reported the error, it might spontaneously revert to "Testing Motors" and then get stuck in a loop.  At this point it just runs the motor test over and over without any indication of stopping, with a very quick flash of the "Motor Unit Fault" message between tests.  Pressing buttons on the handbox didn't seem to stop it after it got to that.

 

So at this point I think that it must now be lubricated well enough, and maybe always was.  Also I think the HBX cable is probably fine after testing it.  As to why this error still shows up, I can only guess.  Maybe there really is some fault in the motor, or in the handbox or in the solid state components inside the mount.  Maybe something is shaped wrongly or bent or broken that I haven't been able to determine.

 

Anyway, thank you again Bill.  This scope is just going to have to do without its fancy autostar features, I guess, but it's still a pretty neat little package even without the automatic tracking.



#6 MistrBadgr

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Posted 26 December 2015 - 04:26 PM

At this point, I do not have any ideas of things to check out.  Let me do some thinking and checking.

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#7 SweetLew

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Posted 26 December 2015 - 09:28 PM

hi...I love u all :) go space!

#8 SweetLew

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Posted 26 December 2015 - 09:30 PM

That should be the motto for Meade...Go space lol sorrrrrry love youuuu guysssss thanks for being awesome, each and every one of you

#9 MistrBadgr

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Posted 27 December 2015 - 06:28 AM

Hello, SweetLew.

 

Welcome to the forum.  Just to bring you up to speed, this particular unit that I have been trying to help with has been out of production for many years and is well outside any warranty period.

 

Meade provides this forum space to allow Meade users to discuss the use of their scopes and any adventures they might have with them.  Though Meade employees do read posts here from time to time and may occasionally respond, the intent is simply to provide a forum for discussion.  The moderators on this board, including myself, are not Meade employees.  We are just enthusiastic about astronomy and want to help others enjoy the activity.

 

I personally own several mounts of the type with this person's scope and they can work well for the price range and development era that they fall into.  They do, however, break upon occasion and I try to help people make them work, rather than simply purchasing a new mount. 

 

The DS mounts are produced as entry level devices.  As such, some things are not designed or constructed in a way that allows for reasonable repair, in order to keep the cost of the mount in a price range that a beginner would be willing to pay. 

 

I believe the issue with this person's mount is most likely one of those non-repairable items.  The issue most likely has to do with the voltage or amperage sensor that detects motor faults, which are most likely part of the mother board.  The other possibility that comes to mind is a little speed sensor that is cemented onto the motor.  Any repair costs would be relatively the same as purchasing a new mount.  The newer Generation 2 mounts are, in truth, much better.

 

If you have any information that can help this person make his mount work correctly again, please feel free to post.  Your solution to the problem would not only help this person enjoy is scope more, but would also teach me something new that I can use to help others.

 

Best Regards,

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#10 MistrBadgr

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Posted 28 December 2015 - 06:14 AM

I have a little information that I picked up.  It applies to all DS type mounts.  The mounts, once outside of warranty, are not considered repairable by Meade.  While under warranty, if there is a problem with one, the customer simply gets a new mount.  Once the mount is outside warranty, the minimum charge for a repair is $150.  With all the handling and labor being what it is, that is a reasonable number in my view.  Anyone not thinking so needs to take their car in for repair.  The big expense is normally the shop time and not parts.

 

For the DSX mount, a new one can currently be purchased from Meade for $160 (no guarantees on the price tommorow, but that is what it is today).  If you sent in a DSX mount for repair, if they had the parts, the minimum cost would be $150.  You now have an old mount, repaired for at least $150.  Instead, buy a new mount for $160 with no wear and tear.  The new one will be the most recent version of the mount, while your old one does not have the most recent improvements.

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#11 legendre

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Posted 03 January 2016 - 12:35 PM

Howdy All - and First Post.

 

I have the dubious honor of picking up this Meade DSX mount issue from user 'securitah'. He's a pal, and dropped it off at my place last night. Now the hope is that I might be able to correct its errant ways, as I tend to have a knack for that sort of thing.

 

Having done some basic disassembly, it's clear that this is a very 'crude' type of servo system. There are no stepper motors here, just simple brush-type DC motors driving geartrains, with little plastic photo-interrupter wheels running between what must be an IR emitter / detector pair. One device has two leads (emitter) and the other three leads (detector - photo-transistor, perhaps). If there is current-sensing, it's being done on the 'mainboard' which I presume is down inside the base.. haven't gotten that far, yet.

 

Securitah was quite accurate in his description of the behavior. On power-up the mount drives first the vertical and then the horizontal drives, each for about 5' at most, and then reports a Motor Unit Failure. Most ANNOYINGLY it does NOT give a meaningful error code that can be looked up in a table - just a generic message that could mean anything between "Grease is sticky" to "Unit is engulfed in flames". So no help there.

 

All I can verify is that the batteries are quite good, neither drive train sounds or acts as if it's unduly loaded, but the error persists none the less. But lacking a meaningful error message, who's to say what's really wrong? The dopes had enough space to install a very verbose, paragraph-long error message - but came up one byte (?!) short, so no hex code (00-FF) for us!

 

My first question(s) are as follows:

 

1) Which conditions will produce the generic "Motor Unit Fault" message? 

 

2) Has anyone come across any useful info, since the topic was last viewed?

 

FYI, I intend to fix this thing.. or at least make it far enough to understand why I might be unable to fix it (dead motherboard, unavailable parts, etc). Any any all help is definitely appreciated..

 

Thanks folks!

 

Bill in St. Paul


There's a Star-Man waiting in the sky, he'd like to come and meet us but he hasn't got the time..


#12 legendre

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Posted 03 January 2016 - 12:44 PM

One other quick comment..

 

While I have almost thirty years of experience as a general-purpose mechanical / electronic technician, I have ZERO experience with telescopes and astronomy et al. So I ask that you please bear with me as I absorb the basic concepts and standard nomenclature of the field..  shouldn't take too long. ;-)


There's a Star-Man waiting in the sky, he'd like to come and meet us but he hasn't got the time..


#13 MistrBadgr

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Posted 06 January 2016 - 02:44 PM

Hi Bill,

 

The DSX mount that you are working on was not designed for repair, simply for replacement.  They came from China and the people there are very secretive about what they make.  There are no prints, specs on internals, spare parts (other than what you can salvage from scrapped mounts.  The whole thing is pretty much a black box.

 

It is cheaper, both for Meade and for the customer, to simply make a replacement of this mount.  They are built as inexpensively as possible to keep the cost down for people wanting to get into astronomy but do not want to spend a lot of money.

 

In my opinion as a professional mechanical engineer, the basic design is a masterpiece of compromise in materials and methods to get reasonable functionality for the cost.  In fact, if I counted the gear teeth right, detecting the passage of just one of those little interference blades indicates something between 1 and 2 arc seconds of scope movement.  Not bad for a $200 robot.  For the most part, the human using the scope provides feedback, one way or another, to tell the scope how well it is doing.

 

I have gone through these mounts so many times in the past that I could just about take one apart and put it back together in my sleep, but I do not know anything about the electrical side of it.  I do not know of anyone who has become an expert on the electrical internals.  Normally, it is not worth the effort.

 

The most common failures that trash one of these mounts, beyond an occasional electrical component that becomes defective is the scope being toppled over, which breaks the drive shaft in the altitude drive (moves the scope up and down).  There is a relatively weak spot where slots are cut through the bell shaped telescope end of that shaft.  I nut with three legs sticks its legs through those slots to push on a disk to serve as a clutch plate mechanism inside.

 

Most likely, if you figure out what parts are not working, there will be somebody around that has a scope with a broken altitude shaft.  In fact, I think I have a carcass or two that I have scavenged parts off of.

 

If someone has a mount with a broken altitude shaft, but everything else is ok, you might think about taking something like that and putting the good altitude shaft out of the mount you have in it.

 

What you have is a DS-2000 mount, what I call a Generation 1 mount (even though there were several generations and upgrades before it)  There is a Generation 2 mount that is now called a Star Navigator.  The drive shaft in your DSX scope will fit in one of those as well.  The DSX mount you have is the same as a DS-2000 mount with an ell shaped bracket that the little short scope mounts to rather than the round mount ring that larger/longer scopes use.  All you have to do is bolt on the bracket on your scope to a DS 2000 or Star Navigator mount and you are good to go.  The bolt holes are the same.

 

Hope this helps,

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#14 legendre

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Posted 21 February 2016 - 05:11 PM

Bill,

 

Thank you for taking  the time to write such a thoughtful and detailed comment. All of the mechanicals, including the driveshaft you mention, are in splendid shape. As securitah said, this appears to be an NIB scope - though it's possible it's an open-box return, or something along those lines. That is, it may well be a 'new', but returned as defective item. 

 

My gut instinct tells me that we're up against a sensor problem, and I'm betting it's one of the optical (IR) transceiver pairs that watch the slotted wheels. That is, either a dead LED or photodiode in one of the pairs. The movement sensing technique used in this mount is for all practical purposes identical to that used in a conventional ball type computer mouse. And I would not be the least bit surprised to find out that the sensor pairs used in the Meade mount can also be  found in some brands of computer mice.. 

 

Next step would be to attach some probes to the sensors, and determine whether we do or do not have a signal output. A dead LED or photodiode would result in a loss of signal.. But if we do have good signal, then it's down to "broken wires" or - unfortunately - dead pins on the micro. I'm sure there are other potential trouble sources as well, but these are the first that come to mind. 

 

Now, if you know of a source of a busted mount, that could be salvaged with my mechanical parts, that would be simple and ideal. Otherwise, I'd just as well be interested in a pair of sensor boards from a (mechanically) damaged mount.. assuming that's where trouble is found. 

 

Enough for now. Thanks again for your help, and please (anyone) let me know if you have a spare mount that might be suitable for my needs. 

 

-Bill


There's a Star-Man waiting in the sky, he'd like to come and meet us but he hasn't got the time..


#15 legendre

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Posted 21 February 2016 - 05:23 PM

One other quick thought..

 

Is it possible to use this mount in 'manual' mode? That is, driven by the motors & electronics but controlled entirely by the operator pressing buttons on the handheld controller?

 

Again, I know nothing about this field, but it seems that in this mode, the control resolution is awfully coarse.. the minimum angle traversed by the briefest control input seems to be several (many?) minutes of arc, possibly even large fractions of a degree..

 

To me this would seem unsuitable, but then again, I wouldn't quite know..


There's a Star-Man waiting in the sky, he'd like to come and meet us but he hasn't got the time..


#16 MistrBadgr

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Posted 22 February 2016 - 05:51 AM

The little hand controller that works that way is on scopes with the letters "EC" after them.  Even they have control of different speeds.  Let me think about this a bit.


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#17 legendre

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Posted 22 February 2016 - 03:19 PM

Just noticed this..

 

For manual tracking, the slew rates are adjustable in ten steps (0-9), using the hand controller. However, when I select a speed, it only changes the slew rate of the altitude motor - the azimuth motor +always+ runs at full-speed, irrespective of speed setting. 

 

I'm wondering if this is the same fault that the software is identifying as "motor unit failure"? If so, once again, this points to an issue with either the sensor pair, or the motor controller hardware.. it's not getting any slew rate feedback and hence can't determine the speed of the motor. I'd like to hear your thoughts on this, but either way, I'm going to get inside and see what kind of signals I find on each of the two motor / sensor systems. 

 

My hunch is there will be a major difference between what we see on the alt. vs. on the azi. 


There's a Star-Man waiting in the sky, he'd like to come and meet us but he hasn't got the time..


#18 MistrBadgr

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Posted 25 February 2016 - 03:04 PM

If the az drive is always at full speed and the alt seems to work OK, I am thinking you are correct and there is something wrong with the AZ speed sensor on the motor.  There is another name for for that part, but I cannot remember what it is.  It is sort of a pulse counter.

 

Bill


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#19 legendre

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Posted 26 February 2016 - 07:08 PM

Shrug, some type of servo circuit, with closed-loop feedback. 

 

PLL?


There's a Star-Man waiting in the sky, he'd like to come and meet us but he hasn't got the time..





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